Why does my phone alarm change on its own?

I've had this problem with my phones alarm clock for as long as I had it. And it has been nearly 3 years now that I have had it.

It is a Samsung Galaxy S 4 Mini.

I would set my alarms but after one (maybe two or three) days, it would change all by itself. Most commonly it would change when it would go off. I would have it set to go off on weekdays, but when I check a few days later it says it goes off only on Friday or Wednesday, something like that.

Has anyone else experienced this problem and figured out the cause of it? For it is rather irritating, and I am sinerely afraid it may change on my more important days when I NEED it to be set correctly.

Thank you for your time.

Have a wonderful evening.

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